This project is concerned with (a) analyses of the genetic diversity, of Trypanosoma cruzi and its implications to the epidemiology, course and diagnosis of Chagas' disease, (b) the development of high resolution flow cytometry instrumentation for biomedical research and (c) the utilization of flow cytometry and low light level video microscopy for the analyses of infectious agents. We have established that inter-developmental stage differences exist in both total DNA and kinetoplast and/or nuclear base ratios in T. cruzi. Hybridization analyses with DNA probes indicate that T. cruzi exhibits restriction fragment length polymorphism (RFLP) and preliminary data indicate this may be due, in part, to amplified DNA or multiple repeated sequences. Although definitely a low frequency occurrence, variants of T. cruzi can arise spontaneously which may explain both the appearance and maintenance of T. cruzi diversity in nature. Environmental stress can result in the appearance of new and stable variants within cloned stocks.